bet no cap

Is a combination of "Bet" and "No cap".

"Bet" is used In response to a statement.
Slang for Fa sho, which is slang for For sure; which means Sure or Okay.

"No Cap" means that their not lying or capping like they did something.
Sometimes ppl write it like this🙅🏽 ♀️🧢or 🚫🧢 different ways

So together 'Bet no cap' is agreeing to a statement that, that person is telling the truth or not lying. Basically saying yes i agree with that statement.

"hey, that food was good",

"bet no cap"